Integrated circuits associated with multiple output devices often have undesirable output signal fluctuations which are caused by negative ground voltage variations, commonly termed glitches. Many multiple output devices are rapidly switched, which causes excess current to be dumped into the internal ground of the circuitry. The internal ground nodes of such circuits are connected to an external ground node through a package pin which includes an inherent inductance. The external ground is fixed to zero volts. The excess current dumped into the internal ground and the external ground causes both positive and negative internal ground voltage fluctuations as described by the inductor-voltage equation V=L di/dt.
In particular, the negative ground voltage fluctuations, often termed spikes or glitches, cause transistors in the integrated circuitry to prematurely turn on when the transistors' emitters are referenced to internal ground and their bases are referenced to the external voltage supply. When such transistors prematurely turn on, the output of the circuitry often begins to oscillate and creates undesirable output signal fluctuations. Such internal ground voltage fluctuations will become increasingly worse as circuit designers strive to obtain faster switching of multiple output devices.
A need has thus arisen for compensation circuitry which can prevent or eliminate undesirable output signal fluctuations caused by internal ground voltage glitches. In particular, a need has arisen for controlling the effects caused by severe negative internal ground voltage fluctuations created by rapid switching of multiple output devices. Such compensation circuitry should be useful with both transistor and diode input devices, and should be controllable as to the level of compensation control.